scholarly journals A GEOMETRIC PROCESSING WORKFLOW FOR TRANSFORMING REALITY-BASED 3D MODELS IN VOLUMETRIC MESHES SUITABLE FOR FEA

Author(s):  
S. Gonizzi Barsanti ◽  
G. Guidi

Conservation of Cultural Heritage is a key issue and structural changes and damages can influence the mechanical behaviour of artefacts and buildings. The use of Finite Elements Methods (FEM) for mechanical analysis is largely used in modelling stress behaviour. The typical workflow involves the use of CAD 3D models made by Non-Uniform Rational B-splines (NURBS) surfaces, representing the ideal shape of the object to be simulated. Nowadays, 3D documentation of CH has been widely developed through reality-based approaches, but the models are not suitable for a direct use in FEA: the mesh has in fact to be converted to volumetric, and the density has to be reduced since the computational complexity of a FEA grows exponentially with the number of nodes. <br><br> The focus of this paper is to present a new method aiming at generate the most accurate 3D representation of a real artefact from highly accurate 3D digital models derived from reality-based techniques, maintaining the accuracy of the high-resolution polygonal models in the solid ones. The approach proposed is based on a wise use of retopology procedures and a transformation of this model to a mathematical one made by NURBS surfaces suitable for being processed by volumetric meshers typically embedded in standard FEM packages. The strong simplification with little loss of consistency possible with the retopology step is used for maintaining as much coherence as possible between the original acquired mesh and the simplified model, creating in the meantime a topology that is more favourable for the automatic NURBS conversion.

Author(s):  
А.Б. Салтыков ◽  
С.В. Грачев

Редукционистский подход в медицине рассматривает живые системы в качестве закрытых (замкнутых) образований, функции которых полностью детерминированы свойствами соответствующих материальных компонентов. Каждое нарушение функции объясняется предшествующими изменениями структур, реализующих эту функцию. Из этого следует, что любая патология структурно-функциональна по своей сути, а понятие «функциональные заболевания» - принципиально ошибочно из-за искажения причинно-следственных отношений. По мере прогресса медицины ожидается открытие собственно первичных структурных маркеров «функциональных» заболеваний, что будет иметь решающее значение для их ранней диагностики и патогенетического лечения (ориентированного прежде всего, на устранение первичного звена расстройств). Вместе с тем, в медицине существует более общий холистический (функционально ориентированный) подход, формирующий иной стереотип клинического мышления. В этих рамках любая патология объясняется недостаточностью адаптивных функций организма в изменившихся условиях существования. Обычно сложный характер функциональных взаимодействий делает невозможным их описание на основе текущих характеристик материальных компонентов системы, особенно при воздействии на организм внешних патогенных факторов. Именно внешние воздействия способны инициировать первичный дефицит адаптивных механизмов с заведомо вторичными структурными изменениями, что позволяет перестать рассматривать «функциональные болезни» как принципиально ошибочное понятие. Первичный дефицит функций наиболее нагляден при информационной патологии, идеальная природа которой не сводится к соответствующим материальным носителям. Все это ставит под сомнение возможность обнаружения собственно первичных структурных маркеров некоторых заболеваний, особенно если в их основе лежит информационная патология (невроз, нервная анорексия, психическая аменорея, морская болезнь, некоторые формы фантомных болей и др.). Reductionist approach in medicine considers living systems as closed (closed) formations whose functions are completely determined by the properties of the corresponding material components. Each disturbance of the function is explained by previous changes in the structures that realize this function. From this it follows that any pathology is structurally functional in its essence, and the concept of «functional diseases» is fundamentally erroneous because of the distortion of cause-effect relationships. As medicine progresses, the actual primary structural markers of «functional» diseases are expected to be discovered, which will be crucial for their early diagnosis and pathogenetic treatment (primarily aimed at eliminating the primary link of disorders). At the same time, in medicine there is a more general holistic (functionally oriented) approach, forming a different stereotype of clinical thinking. Within this framework, any pathology is due to the lack of adaptive functions of the organism in the changed conditions of existence. Usually the complex nature of functional interactions makes it impossible to describe them on the basis of the current characteristics of the material components of the system, especially when external pathogenic factors influence the organism. It is external actions that can initiate a primary deficit of adaptive mechanisms with known secondary structural changes, which allows us to stop treating «functional diseases» as a fundamentally wrong concept. The primary deficit of functions is most evident in information pathology, the ideal nature of which is not reduced to the corresponding material carriers. All this calls into question the possibility of detecting the primary structural markers of certain diseases, especially if they are based on information pathology (neurosis, anorexia nervosa, mental amenorrhea, seasickness, some forms of phantom pains, etc.).


2016 ◽  
Vol 97 ◽  
pp. 153-158 ◽  
Author(s):  
Elena Mihalache ◽  
Bogdan Pricop ◽  
Radu Ioachim Comăneci ◽  
Marius Gabriel Suru ◽  
Nicoleta Monica Lohan ◽  
...  

Fe-14Mn-6Si-9Cr-5Ni (wt. %) shape memory alloys (SMAs) were produced by powder metallurgy (PM) combined with Mechanical Alloying (MA). The specimens were pressed and sintered under Ar atmosphere from as blended powders as well as from mixtures of as blended and 10, 20, 30 and 40 vol. % MA’ed powders, respectively. The five groups of sintered specimens were hot-rolled, spark-erosion cut and solution treated at five temperatures (923, 1023, …, 1373K/ 300 s/ water). Tensile loading-unloading tests were performed in order to obtain stress-induced martensite at different pre-straining degrees. The static responses of the twenty five types of specimens were evaluated by means of the surface areas under unloading curve (E2) and between loading and unloading curves (E1) which were used for determining static internal friction, Q-1. The dynamic responses of the undeformed specimens were determined by Dynamic Mechanical Analysis (DMA) performed at room temperature with a three-point-bending specimen holder in strain sweep mode. The structure of the twenty five specimens was analyzed X-ray diffraction. The effects of MA fraction were correlated with static and dynamic responses via structural changes.


Author(s):  
D. Einaudi ◽  
A. Spreafico ◽  
F. Chiabrando ◽  
C. Della Coletta

Abstract. Rebuilding the past of cultural heritage through digitization, archiving and visualization by means of digital technology is becoming an emerging issue to ensure the transmission of physical and digital documentation to future generations as evidence of culture, but also to enable present generation to enlarge, facilitate and cross relate data and information in new ways. In this global effort, the digital 3D documentation of no longer existing cultural heritage can be essential for the understanding of past events and nowadays, various digital techniques and tools are developing for multiple purposes.In the present research the entire workflow, starting from archive documentation collection and digitization to the 3D models metrically controlled creation and online sharing, is considered. The technical issues to obtain a detail 3D model are examined stressing limits and potentiality of 3D reconstruction of disappeared heritage and its visualization exploiting three complexes belonging to 1911 Turin World’s Fair.


Author(s):  
S. Artese ◽  
J. L. Lerma ◽  
J. Aznar Molla ◽  
R. M. Sánchez ◽  
R. Zinno

<p><strong>Abstract.</strong> The three-dimensional (3D) documentation and surveying of cultural heritage can be carried out following several geomatics techniques such as laser scanning and thermography in order to detect the original 3D shape after applying reverse engineering solutions. In almost all cases, the integration of data collected by different instruments is needed to achieve a successful and comprehensive 3D model of the as-built architectural shape of the historical building. This paper describes the operations carried out by the authors to determine the as-built 3D model of the Escuelas Pias Church, related namely to the dome and circular nave. After the description of the church and historical notes, attention will be driven to the indirect registration results obtained with three different laser scanning software packages, highlighting similarities and differences, and the consequences while generating meshes. The 3D model carried out will then be described and the results of some investigations with regard to the hypotheses about the design of the dome and the origin of the alterations will be presented.</p>


2021 ◽  
Author(s):  
Martin Hložek ◽  
Markéta Tymonová ◽  
Vojtěch Nosek ◽  
Zdeňka Měchurová ◽  
Petr Holub ◽  
...  

The publication is focused on late medieval pottery products with higher aesthetical effect. The key group is represented by stove tiles, where the unifying elements of relief decoration helped to define series of motifs for stoves with specific iconographic concept, which were found in various locations. The same approach can be also used with small ceramic sculptures, aquamaniles and relief-decorated floor tiles, even though the achieved information value in these cases is much lower. Micropetrographic, XRF and other analyses helped to identify the production centres and the distribution model of these ceramic groups. 3D documentation enabled a detailed comparison of differences between individual reliefs and specific traces of manufacturing procedures. Individual chapters contain active links to the source database of analysed items and to 3D models of selected specimens from reference collections.


Author(s):  
M. Pulcrano ◽  
S. Scandurra ◽  
E. Fragalà ◽  
D. Palomba ◽  
A. di Luggo

Abstract. The paper presents the results of a research carried out on the Church of Santa Maria degli Angeli in Pizzofalcone in Naples, in which multi-sensor surveys have been performed in order to assess the architectonical, geometrical and colorimetric characteristics of the majestic basilica. The use of integrated technologies made it possible to realize 3D digital models that allowed the complete representation of the building, integrating data and filling the gaps of the different previous surveys. The performances of the various reality-based technologies employed have been subjected to critical analysis in order to maximize their potential, optimize survey and data elaboration phases, and obtain the expected results. These latter have been defined through the derived digital re-elaborations and representations. Hence, the objective of the research is to carry out a comparative analysis on the 3D models generated through the different active and passive sensors employed in order to proceed with their integration and achieve an accurate, original and updated methodology of building survey.


Author(s):  
Zheyang Wu ◽  
Chun Yang ◽  
Dalin Tang

It has been hypothesized that mechanical risk factors may be used to predict future atherosclerotic plaque rupture. Much progress has been made in computational modeling, medical imaging, and mechanical analysis for atherosclerotic plaque vulnerability assessment in recent years [1–2]. However, truly predictive methods to predict plaque rupture are currently lacking in the literature and practice. In this paper, we introduce a procedure using computational and statistical models based on serial magnetic resonance imaging (MRI) to quantify sensitivity and specificity of mechanical predictors and their combinations to identify the best candidate for rupture prediction. Serial MRI of carotid plaque from a patient with follow-up scan showing ulceration (rupture) was acquired and the actual appearance of ulceration was used as “gold standard” and validation for the predictive method.


2012 ◽  
Vol 562-564 ◽  
pp. 1487-1491
Author(s):  
Mei Chen ◽  
Fei Zheng ◽  
Na Li

The mechanical errors in a mobile waveguide slot array antenna will finally influence the electromagnetic performances. Hence it is necessary to understand the relationship between them, which requires mechanical-electromagnetic analyses. The 3D models in both mechanical analysis and electromagnetic analysis are greatly different. They need a precise connection and transformation. The paper proposes an effective 3D model transformation method. From 3D geometric model to 3D mechanical model, and then to 3D electromagnetic model, the precise connection and transformation can be finished. It can be used to increase the analysis precision of a complex waveguide slot array antenna.


Author(s):  
O. Al Khalil ◽  
P. Grussenmeyer

<p><strong>Abstract.</strong> The paper explores the possibilities of using old images for 2D and 3D documentation of archaeological monuments using open source, free and commercial photogrammetric software. The available images represent the external façade of the Western gate and Al Omari Mosque in the city of Bosra al-Sham in Syria, which were severely damaged during the recent war. The images were captured using consumer camera and they were originally used to achieve 2D documentation for each part of the gate separately. 2D control points were used to scale the digital photomosaic and reference distances were applied for the scaling of the 3D models. Archive images were used to produce a 2D digital photomosaic of the monument by image rectification and 3D dense point clouds by applying Structure from Motion (SfM) techniques. The geometric accuracy of the results has been assessed.</p>


2019 ◽  
Vol 61 (7) ◽  
pp. 1386
Author(s):  
В.М. Егоров ◽  
П.Н. Якушев ◽  
М.А. Арсентьев ◽  
А.С. Смолянский

V. M. Egorov1, P. N. Yakushev1, M. A. Arsentiev2,3, A.S. Smoliansky2,3. 1Ioffe Institute, Russian Academy of Sciences, St. Petersburg, Russia 2 Branch of JSC Karpov NIFHI, Moscow, Russia 3 Mendeleev University of Chemical Technology, Moscow, Russia A comparative analysis for the melting of Polytetrafluoroethylene both in the initial and irradiated state and for composition with 1% "green" silica has been carried out. The method of Dynamic Mechanical Analysis was used to characterize the glass transitions for all compositions studied. The calculation based on the smeared first-order phase transition theory for the contours of the thermal capacity peaks made it possible to reveal the features of structural changes in the composite and in the irradiated Polytetrafluoroethylene.


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